1. Field of the Invention
The present invention relates to a piston for an internal combustion engine, an internal combustion engine including this piston, and a manufacturing method of this piston.
2. Description of Related Art
A conventional piston for an internal combustion engine is disclosed, for example, in Japanese Patent Application Publication No. 2009-243355, in which a heat-shielding film having a lower thermal conductivity than a piston base material and having a lower heat capacity per unit volume than the piston base material is formed on the upper surface of a land part. A heat-shielding film having such thermal properties allows the temperature of the upper surface of the land part to follow the temperature of a working medium inside a cylinder of an internal combustion engine. That is, during the combustion stroke of the internal combustion engine, the temperature of the upper surface of the land part can be increased, while during the intake stroke, the temperature of the upper surface can be lowered. Thus, it is possible to improve the fuel efficiency by reducing cooling loss during the combustion stroke, and to suppress occurrence of knocking or abnormal combustion due to heating of the working medium during the intake stroke.
Another piston for an internal combustion engine is disclosed in Japanese Patent Application Publication No. 11-280545, in which a ferrous metal material having a lower thermal diffusivity than a piston base material (specifically, an aluminum alloy) is provided to the side surface of a land part. Providing a metal material having such thermal properties can increase the temperature around the metal material. Thus, it is possible to improve the combustion efficiency of the internal combustion engine by promoting the evaporation and gasification of a liquid fuel adhering to or around the surface of the metal material.